According to recent research published in the International Journal of Sport Nutrition and Exercise Metabolism, consuming coffee (or another source of caffeine) an hour before your workout can help you burn about 15 percent more calories post-sweat session than you would otherwise. Here's why: Caffeine is a natural stimulant that can increase your respiratory rate, your metabolism, and the amount of adrenaline in your bloodstream. Although research has already shown that consuming the stuff before a workout can help you work harder and longer than normal, researchers in this study found that the calorie-burning benefits of caffeine can last up to three hours after you’ve left the gym.

Researchers in Spain studied 12 men and women who typically worked out for about an hour, four to seven times a week. An hour before their workout, participants were given either a placebo or a caffeine dosage of 0.5, 1.5, 3.0, or 4.5 milligrams per kilogram of body weight. After downing the dosage, study participants exercised at an intermediate effort level for an hour and then rested for three hours. While they were resting, researchers measured their heart rate, blood pressure, and respiration. The study revealed that the ideal metabolism-boosting amount of caffeine was 4.5 milligrams per kilogram of body weight—or about 12-ounces of brewed coffee for a 150-pound person (that's the size of a tall coffee at Starbucks).

More good news: The researchers noted that, while this study only examined the effects of caffeine on metabolism after endurance training, previous research has shown that the same amount burns 15 percent more calories up to 75 minutes after resistance training. So if you're looking for an easy way to burn extra cals, go ahead and have some coffee before your workout—it may help you drop a jean size faster.